#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>

void error_handling(char *message);

int main(int argc, char * argv[])
{
  int serv_sock;
  int clnt_sock;

  struct sockaddr_in serv_addr;
  struct sockaddr_in clnt_addr;
  socklen_t clnt_addr_size;

  char message[] = "Hello World!";
  
  if (argc != 2)
  {
    printf("Usage: %s <port> \b", argv[0]);
    exit(1);
  }

  serv_sock = socket(PF_INET, SOCK_STREAM, 0);
  if (serv_sock == -1)
    error_handling("socket() error!");
  
  memset(&serv_addr, 0, sizeof(serv_addr));
  serv_addr.sin_family = AF_INET;
  serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
  serv_addr.sin_port = htons(atoi(argv[1]));

  if (bind(serv_sock, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) == -1)
    error_handling("bind() error!"); 

  if (listen(serv_sock, 5) == -1)
    error_handling("listen() error!");
  
  clnt_addr_size = sizeof(clnt_addr);
  clnt_sock = accept(serv_sock, (struct sockaddr *) &clnt_addr, &clnt_addr_size);
  if (clnt_sock == -1)
    error_handling("accept() error!");

  write(clnt_sock, message, sizeof(message));
  close(clnt_sock);
  close(serv_sock);
  return 0;
}

void error_handling(char *message)
{
  fputs(message, stderr);
  fputs("\n", stderr);
  exit(1);
}
